External evaluation of regional cardiac lymph drainage in intact dogs

After coronary occlusion, interruption of cardiac lymphatic flow reduces the proportion of creatine kinase depleted from the heart appearing in blood. Accordingly, characterization of cardiac lymph flow should be helpful in refining enzymatic estimates of infarct size. In the present study, 99mTc-sulfur colloid, a potential tracer for imaging cardiac lymphatic structures, was injected intramurally into selected regions of the heart in 17 dogs. Serial images of the chest were obtained for 24 hours with a scintillation camera, after which the animals were killed and the cardiac and other mediastinal nodes removed and assayed for radioactivity. Analysis of the images and counts in vitro demonstrated a consistent drainage pathway between the anterior left ventricular wall and the cardiac node. Other areas of the heart exhibited variable drainage patterns. After injection into the anterior left ventricular wall, in both open-chest dogs (n = 3) and in closed-chest dogs via a percutaneous, subxiphoid approach (n = 3) with a specially designed, collared needle, the cardiac node was visualized within 2 minutes. Activity in the cardiac node region reached a peak within 40 minutes in five of six dogs and accumulated greater than 1000 counts/min in five of six dogs before plateauing. In three additional dogs subjected to cardiac lymphatic occlusion five or six days prior to anterior left ventricular injection, appearance of radioactivity in the cardiac node was markedly delayed and maximum activity was far less than that in controls. Thus, regional cardiac lymph flow from the anterior left ventricular wall can be assessed semiquantitatively with a radionuclide imaging technique, potentially useful in refinement of enzymatic estimates of infarct size.